Merge pull request #1310 from Taneb/knownstatus

Add KnownStatus typeclass

servant/servant.cabal

@@ -55,6 +55,7 @@ library
     Servant.API.RemoteHost
     Servant.API.ReqBody
     Servant.API.ResponseHeaders
+    Servant.API.Status
     Servant.API.Stream
     Servant.API.Sub
     Servant.API.TypeLevel

servant/src/Servant/API/Status.hs

@@ -0,0 +1,155 @@
+{-# LANGUAGE DataKinds #-}
+-- Flexible instances is necessary on GHC 8.4 and earlier
+{-# LANGUAGE FlexibleInstances #-}
+module Servant.API.Status where
+
+import Network.HTTP.Types.Status
+import GHC.TypeLits
+
+-- | Witness that a type-level natural number corresponds to a HTTP status code
+class KnownNat n => KnownStatus n where
+  statusVal :: proxy n -> Status
+
+instance KnownStatus 100 where
+  statusVal _ = status100
+
+instance KnownStatus 101 where
+  statusVal _ = status101
+
+instance KnownStatus 200 where
+  statusVal _ = status200
+
+instance KnownStatus 201 where
+  statusVal _ = status201
+
+instance KnownStatus 202 where
+  statusVal _ = status202
+
+instance KnownStatus 203 where
+  statusVal _ = status203
+
+instance KnownStatus 204 where
+  statusVal _ = status204
+
+instance KnownStatus 205 where
+  statusVal _ = status205
+
+instance KnownStatus 206 where
+  statusVal _ = status206
+
+instance KnownStatus 300 where
+  statusVal _ = status300
+
+instance KnownStatus 301 where
+  statusVal _ = status301
+
+instance KnownStatus 302 where
+  statusVal _ = status302
+
+instance KnownStatus 303 where
+  statusVal _ = status303
+
+instance KnownStatus 304 where
+  statusVal _ = status304
+
+instance KnownStatus 305 where
+  statusVal _ = status305
+
+instance KnownStatus 307 where
+  statusVal _ = status307
+
+instance KnownStatus 308 where
+  statusVal _ = status308
+
+instance KnownStatus 400 where
+  statusVal _ = status400
+
+instance KnownStatus 401 where
+  statusVal _ = status401
+
+instance KnownStatus 402 where
+  statusVal _ = status402
+
+instance KnownStatus 403 where
+  statusVal _ = status403
+
+instance KnownStatus 404 where
+  statusVal _ = status404
+
+instance KnownStatus 405 where
+  statusVal _ = status405
+
+instance KnownStatus 406 where
+  statusVal _ = status406
+
+instance KnownStatus 407 where
+  statusVal _ = status407
+
+instance KnownStatus 408 where
+  statusVal _ = status408
+
+instance KnownStatus 409 where
+  statusVal _ = status409
+
+instance KnownStatus 410 where
+  statusVal _ = status410
+
+instance KnownStatus 411 where
+  statusVal _ = status411
+
+instance KnownStatus 412 where
+  statusVal _ = status412
+
+instance KnownStatus 413 where
+  statusVal _ = status413
+
+instance KnownStatus 414 where
+  statusVal _ = status414
+
+instance KnownStatus 415 where
+  statusVal _ = status415
+
+instance KnownStatus 416 where
+  statusVal _ = status416
+
+instance KnownStatus 417 where
+  statusVal _ = status417
+
+instance KnownStatus 418 where
+  statusVal _ = status418
+
+instance KnownStatus 422 where
+  statusVal _ = status422
+
+instance KnownStatus 426 where
+  statusVal _ = status426
+
+instance KnownStatus 428 where
+  statusVal _ = status428
+
+instance KnownStatus 429 where
+  statusVal _ = status429
+
+instance KnownStatus 431 where
+  statusVal _ = status431
+
+instance KnownStatus 500 where
+  statusVal _ = status500
+
+instance KnownStatus 501 where
+  statusVal _ = status501
+
+instance KnownStatus 502 where
+  statusVal _ = status502
+
+instance KnownStatus 503 where
+  statusVal _ = status503
+
+instance KnownStatus 504 where
+  statusVal _ = status504
+
+instance KnownStatus 505 where
+  statusVal _ = status505
+
+instance KnownStatus 511 where
+  statusVal _ = status511